钛基片的化学机械抛光技术研究

采用化学机械抛光（CMP）方法对钛基片进行纳米级平坦化处理,通过系列抛光试验优化抛光液组成和抛光工艺条件后,得到AFM-Ra为0.159 nm的纳米级抛光表面和156.5 nm/min的抛光速率。抛光液的电化学分析结果表明：二氧化硅颗粒和乳酸在钛表面有不同程度的吸附缓蚀作用,氨水和F-的络合、扩散作用能破坏缓蚀膜层,两者的中间平衡状态才能得到最佳抛光效果。抛光后钛表层XPS测试结果显示钛表层经过化学氧化形成疏松氧化层后,再通过磨粒和抛光垫的机械作用去除。     

纯铅化学机械抛光中工艺参数对抛光性能的影响

为获得高质量纯铅表面,采用化学机械抛光(CMP)的方法并辅以自制抛光液,研究了胶体二氧化硅抛光颗粒的形状、粒径和浓度、加载压力、抛光头与抛光盘转向和转速、抛光液流量等工艺参数对铅片表面材料去除率和粗糙度的影响. 研究表明:小粒径异形(眉形)胶体二氧化硅抛光颗粒相较于大粒径球形颗粒更有利于铅片抛光,抛光颗粒的粒径和浓度对纯铅抛光性能的影响主要取决于铅片表面与胶体二氧化硅颗粒以及抛光垫表面丝绒的耦合作用关系. 随着加载压力、抛光头与抛光盘转向和转速、抛光液流量的改变,铅片表面和抛光垫之间驻留的层间抛光液的厚度以及状态发生改变,从而直接影响抛光液的流动性、润滑性和分散性,以及影响抛光颗粒和化学试剂与铅片表面的机械化学作用,进而影响抛光质量和材料去除率. 通过对工艺参数影响的研究和对工艺参数的优化,最终获得了表面粗糙度R_a为1.5 nm的较为理想的超光滑纯铅表面,同时材料去除率能够达到适中的380 ?/min.      

Dual emission laser induced fluorescence for direct planar scalar behavior measurements

 In this paper, a new method of measuring scalar behavior in bulk aqueous fluid flows is presented. Using a simple ratiometric scheme, laser induced fluorescence from organic dyes can be normalized so that direct measurements of a scalar in the flow are possible. The technique dual emission laser induced fluorescence (DELIF) relies on normalizing the fluorescence emission intensity of one dye with the fluorescence emission intensity of a second dye. Since each dye fluoresces at a different wavelength, one can optically separate the emission of each dye. This paper contains an overview of the basic ratiometric technique for pH and temperature measurements as well as the spectral properties of nine water soluble dyes. It also covers the three most significant sources of error in DELIF applications. To demonstrate the technique, steady state turbulent jet mixing and temperature fields in a thermal plume were quantified. The accuracy was camera limited at under 3% of the fluorescence ratio which corresponds to 0.1 pH units or 1.8 °C. Received 7 June 1996/Accepted 17 June 1997     

Liquid film characterization in horizontal,annular, two-phase,gas–liquid flow using time-resolved laser-induced fluorescence

A non-intrusive optical technique was developed to provide time-resolved longitudinal and cross-sectional images of the liquid film in horizontal annular pipe flow of air and water, revealing the interfacial wave behavior. Quantitative information on the liquid film dynamics was extracted from the time-resolved images. The planar laser-induced fluorescence technique was utilized to allow for optical separation of the light emitted by the film from that scattered by the air–water interface. The visualization test section was fabricated from a tube presenting nearly the same refractive index as water, which allowed the visualization of the liquid film at regions very close to the pipe wall. Longitudinal images of the liquid film were captured using a high-frame-rate digital video camera synchronized with a high-repetition-rate laser. An image processing algorithm was developed to automatically detect the position of the air–water interface in each image frame. The thickness of the liquid film was measured at two axial stations in each processed image frame, providing time history records of the film thickness at two different positions. Wave frequency information was obtained by analyzing the time-dependent signals of film thickness for each of the two axial positions recorded. Wave velocities were measured by cross-correlating the amplitude signals from the two axial positions. For the film cross-section observations, two high-speed digital video cameras were used in a stereoscopic arrangement. Comparisons with results from different techniques available in literature indicate that the technique developed presents equivalent accuracy in measuring the liquid film properties. Time-resolved images of longitudinal and cross-section views of the film were recorded, which constitute valuable information provided by the technique implemented.     

氧化硅/氧化铁复合磨粒用于硬盘基片的抛光研究

本文以HNO3、NaOH、Fe(NO3)3和SiO2浆料为原料,采用沉淀法制备了1种SiO2/Fe2O3复合磨粒,通过X射线衍射仪(XRD)、飞行时间二次离子质谱仪(TOF-SIMS)和扫描电子显微镜(SEM)对其结构进行表征,结果表明Fe2O3包覆到SiO2的表面,复合粒子具有很好的分散性.用UNIPOL-1502抛光机研究了所制备复合磨粒在镍磷敷镀的硬盘基片中的抛光性能,抛光后硬盘基片的表面粗糙度Ra由抛光前的8.87nm降至3.73nm;抛光后表面形貌的显微镜观测结果表明新制备的复合磨粒表现出较好的抛光性能.     

CMP流场的数值模拟及离心力影响分析

化学机械抛光(chemical mechanical polishing,CMP)是一项融合化学分解和机械力学的工艺, 其中包含了流体动力润滑的作用.在已有润滑方程的基础上, 提出并分析了带有离心力项的润滑方程.利用Chebyshev加速超松弛技术对有离心力项的润滑方程进行求解,得到离心力对抛光液压力分布的影响. 数值模拟结果表明,压力分布与不带离心力项的润滑方程得出的明显不同;无量纲载荷和转矩随中心膜厚、转角、倾角、抛光垫旋转角速度等参数的变化趋势相同,但数值相差较大, 抛光垫旋转角速度越大差别越大.      

抛光垫特性及其对300mm晶圆铜化学机械抛光效果的影响研究

利用扫描电子显微镜和接触式表面形貌仪分析了IC1000/Suba-IV和IC1010两种商用抛光垫的主要特性,并通过自行研制的超低压力化学机械抛光(CMP)试验机、四探针测试仪和三维白光干涉仪等研究了这两种抛光垫对300 mm晶圆铜互连的CMP材料去除率、片内非均匀性、碟形凹陷和腐蚀的影响规律.结果表明:IC1010比IC1000的硬度低、压缩率高、粗糙度大,IC1000为网格状沟槽、沟槽较宽、分布较稀,IC1010为同心圆沟槽、沟槽较细、分布较密;相同条件下IC1010比IC1000的材料去除率大、片内非均匀性好;在相同线宽下IC1000与IC1010的腐蚀几乎一致,IC1010的碟形凹陷比IC1000的略大.     

An extra-thin light sheet technique used to investigate meniscus shapes by laser induced fluorescence

A light sheet technique is described to accurately (50 m) measure meniscus profiles in film formation problems. The use of a slit to create the thin (0.1 mm) laser sheet makes the technique easy to implement, and allows tunable sheet thickness. The low light intensity obtained through the slit is compensated by the induced fluorescence of the tested fluid, which provides good picture contrast. After video recording through a microscope, the actual meniscus is recovered by image processing and proper calibration. The efficiency of the technique is demonstrated on a coating flow experiment. Due to its good accuracy and ease of use, this technique is expected to provide useful quantitative information about meniscus problems, in particular for the validation of CFD solutions of coating flows.     

A parametric study of laser induced thin film spallation

We report parametric studies of elastic wave generation by a pulsed laser and associated spalling of thin surface films by the corresponding high stresses. Two different substrate materials, single crystal Si (100) and fused silica, are considered. Spallation behavior of Al thin films is investigated as a function of substrate thickness, film thickness, laser energy, and various parameters governing the source. Surface displacement due to the stress wave is measured by Michaelson interferometry and used to infer the stresses on the film interface. Consistent with previous studies, the maximum stress in the substrate and at the film/substrate interface increases with increasing laser fluence. For many of the conditions tested, the substrate stress is large enough to damage the Si. Moreover, the maximum interface stress is found to increase with increasing film thickness, but decrease with increasing substrate thickness due to geometric attenuation. Of particular significance is the development of a decompression shock in the fused sillica substrates, which results in very high tensile stresses at the interface. This shock enhances the failure of thin film interfaces, especially in thicker samples.     

考虑对流效应和磁场的CMP模型及其数值模拟

推导了具有对流效应的化学机械抛光(chemical mechanical polishing,CMP)润滑模型,研究各参数对压力场分布的影响.在此模型基础上,研究了磁流体抛光液在外界磁场作用下的润滑模型,以及外磁场对抛光过程中压力场分布的影响. 数值结果表明,具有对流效应的润滑模型的压力分布与已有经验结果更一致,能更为有效地解释CMP过程中的负压现象; 进一步通过外界磁场的作用, 可以有效地改变磁流体CMP的压力分布,这为实现对晶片的全局抛光提供了一种可供参考的新途径.      

Local thickness and wave velocity measurement of wavy films with a chromatic confocal imaging method and a fluorescence intensity technique

This work presents two different methods for measuring the thickness of wavy films. The first one is a new non-intrusive technique called “chromatic confocal imaging method” which uses two optical properties—the confocal image and the chromatic aberration of a lens. The accuracy of this technique depends on the optical components, the local gradient of the film thickness and the accuracy of the refractive index used. The second method for simultaneous measurements of film thickness and wave velocity is based on a fluorescence intensity technique. Film thickness and wave velocity measurements of silicone films with different viscosities are presented for Reynolds numbers from 2 to 700 and various inclination angles. The experimental data agree well with the results from published experimental and theoretical studies.     

Multiscale computations of thin films in multiphase flows

In multiphase flows thin films are often encountered when fluid masses collide. These films can become very thin and in direct numerical simulations (DNS) it is often impractical to resolve their thickness fully, even with adaptive grid refining. Here we examine the collision of a fluid drop with a wall and develop a multiscale approach to compute the flow in the film between the drop and the wall. By using a semi-analytical model for the flow in the film we capture the evolution of films thinner than the grid spacing reasonably well.     

A laser induced fluorescence technique for quantifying transient liquid fuel films utilising total internal reflection

This paper describes the development of a laser induced fluorescence (LIF) technique to quantify the thickness and spatial distribution of transient liquid fuel films formed as a result of spray–wall interaction. The LIF technique relies on the principle that upon excitation by laser radiation the intensity of the fluorescent signal from a tracer like 3-pentanone is proportional to the film thickness. A binary solution of 10% (v/v) of 3-pentanone in iso-octane is used as a test fuel with a Nd:YAG laser as the excitation light source (utilising the fourth harmonic at wavelength 266 nm) and an intensified CCD camera is used to record the results as fluorescent images. The propagation of the excitation laser beam through the optical piston is carefully controlled by total internal reflection so that only the fuel film is excited and not the airborne droplets above the film, which had been previously shown to induce significant error. Other known sources of error are also carefully minimised. Calibrated temporally resolved benchmark results of a transient spray from a gasoline direct injector impinging on a flat quartz crown under atmospheric conditions are presented, with observations and discussion of the transient development of the fuel film. The calibrated measurements are consistent with previous studies of this event and demonstrate the applicability of the technique particularly for appraisal of CFD predictions. The potential utilisation of the technique under typical elevated ambient conditions is commented upon.     

基于分子量级的化学机械抛光界面动力学模型研究

考虑抛光液/芯片的相界面氧化剂浓度和芯片氧化薄膜缺陷对材料去除机理的影响,提出化学机械抛光(CMP)中材料去除机理的量级估算方法,应用化学动力学及传质学等理论估算氧化薄膜的扩散深度量级和生成速率,采用纳米压痕仪模拟单个磨粒在芯片表面的压痕作用,应用线性回归方法分析载荷70 nN下,磨粒压入芯片的深度量级为10-11 m.结合模型估算,证实了CMP材料去除机理为单分子层去除机理.结果表明,减小氧化膜厚度可以提高材料去除率,估算结果与他人试验结果相吻合.为进一步研究CMP单分子层材料去除机理提供了理论依据.     

A displaced-line velocity diagnostic and its application in a visualization engine

A technique for measuring three-dimensional velocity by imaging the displacement of a marked fluid line is described, together with its use in an automotive visualization engine. In a flow seeded with 2–3 μ phosphorescing particles, a line is excited by a UV laser beam, deformed by the local velocity field, and detected by stereo low-light-level video cameras. The derivation of velocity from digitized images is discussed and capabilities of the diagnostic are assessed. Some image data taken in the engine are shown and quantitative two-component velocity plots along the line are presented.     

Whole field measurement of temperature in water using two-color laser induced fluorescence

 A technique is described that measures the instantaneous three-dimensional temperature distribution in water using two-color laser-induced fluorescence (LIF). Two fluorescent dyes, Rhodamine B and Rhodamine 110, are used as temperature indicators. A laser light sheet scanned across the entire measurement volume excites the fluorescent dye, and an optical system involving a color beam splitter gives the intensity distribution of the individual fluorescent dyes on two separate monochrome CCD cameras. The ratio of these fluorescence intensities at each point of the image is calibrated against the temperature to eliminate the effect of the fluctuation of illuminating light intensity. A stable thermally stratified layer was measured by this system to evaluate the total accuracy of the measurement system. The random error of the measurement was ±1.4 K with 95% confidence. Measurements of thermal convection over a heated horizontal surface show temperature iso-surfaces having typical structures such as plumes, ridges and thermals. Received: 1 October 1997/Accepted: 23 March 1998     

Concentration flux measurements of a scalar quantity in turbulent flows

A method for determination of velocity-concentration fluxes is presented that combines two conventional imaging techniques, particle image velocimetry (P.I.V.) and planar laser-induced fluorescence (P.L.I.F.). The passive concentration jet was a perfect mixture of fluorescein dye and solid particles submerged in an isotropic homogeneous turbulent channel. The light intensity fluoresced by the dye and the light intensity scattered by the particles were recorded separately on two synchronized cameras by using appropriate high and low-pass filters. Two different sets of images were thus obtained simultaneously. Once digitized and numerically processed, they provide the space and time evolution of velocity and concentration instantaneous fields. Thus, the velocity-concentration correlations can easily be determined. The statistical results for velocity and concentration are compared with classical results in order to validate the technique. We finally report some results giving velocity-concentration fluxes.     

Simultaneous velocity field measurements in two-phase flows for turbulent mixing of sprays by means of two-phase PIV

This paper describes a novel derivative of the PIV method for measuring the velocity fields of droplets and gas phases simultaneously using fluorescence images rather than Mie scattering images. Two-phase PIV allows the simultaneous and independent velocity field measurement of the liquid phase droplets and ambient gas in the case of two-phase flow mixing. For phase discrimination, each phase is labelled by a different fluorescent dye: the gas phase is seeded with small liquid droplets, tagged by an efficient fluorescent dye while the droplets of the liquid phases are tagged by a different fluorescent dye. For each phase, the wavelength shift of fluorescence is used to separate fluorescence from Mie scattering and to distinguish between the fluorescence of each phase. With the use of two cross-correlation PIV cameras and adequate optical filters, we obtain two double frame images, one for each phase. Thus standard PIV or PTV algorithms are used to obtain the simultaneous and independent velocity fields of the two phases. Because the two-phase PIV technique relies on the ability to produce two simultaneous and independent images of the two phases, the choice of the labelling dyes and of the associated optical filter sets is relevant for the image acquisition. Thus a spectroscopic study has been carried out to choose the optimal fluorescent dyes and the associated optical filters. The method has been evaluated in a simple two-phase flow: droplets of 30–40 μm diameter, produced by an ultrasonic nozzle are injected into a gas coflow seeded with small particles. Some initial results have been obtained which demonstrate the potential of the method.     

A film flow model for analysing gravity-driven,thin wavy fluid films

To analyse the physics underlying gravity-driven runoff of thin wavy films, a film flow model is developed, and is solved with computational fluid dynamics. This model is based on the lubrication theory, and takes into account the gravitational, wall shear and surface tension forces. A key characteristic of the model is that it assumes only one computational cell over the film height, which enables studying film flow on larger computational domains. A main aim of this study is to perform a detailed validation of the numerical model. The film flow model is validated against several experiments of gravity-driven, thin fluid films on smooth surfaces. The time-averaged film thickness and the fluid speed profiles predicted by the model show very good agreement with experimental results. Similarly, the film flow model is able to predict the wave speeds with sufficient accuracy. The energy spectra of the waves, where higher frequency waves are present in film flows at higher Reynolds numbers, show an exponentially decaying trend at these high frequencies. The model performs better than the Nusselt equation for film flows, which under-predicts the time-averaged film thickness and over-predicts the time-averaged fluid speeds, even for flows at low Reynolds numbers. The film flow model is compared qualitatively for fingering behaviour. This model also allows to investigate film flows on large surfaces, which can be rough, curved and of complex geometrical shape.     

Spontaneous instability of soft thin films on curved substrates due to van der Waals interaction

The linear bifurcation theory is used to investigate the stability of soft thin films bonded to curved substrates. It is found that such a film can spontaneously lose its stability due to van der Waals or electrostatic interaction when its thickness reduces to the order of microns or nanometers. We first present the generic method for analyzing the surface stability of a thin film interacting with the substrate and then discuss several important geometric configurations with either a positive or negative mean curvature. The critical conditions for the onset of spontaneous instability in these representative examples are established analytically. Besides the surface energy and Poisson's ratio of the thin film, the curvature of the substrate is demonstrated to have a significant influence on the wrinkling behavior of the film. The results suggest that one may fabricate nanopatterns or enhance the surface stability of soft thin films on curved solid surfaces by modulating the mechanical properties of the films and/or such geometrical properties as film thickness and substrate curvature. This study can also help to understand various phenomena associated with surface instability.